17hp 5 speed shifter kart plan

[huseyinozsut]

Hi,

We are three friends trying to build a go kart here in Turkey. In Turkey there are several go kart producers, planty of parts and infinately many used motorcycle and car parts (mainly european and japan). But all of the parts are in EU standards. (For example we can't find a 6" rim, or 12-8-6 tire, standard is 11-7.1-5)

We bought a 2 cylinder, 4 stroke, 250cc, 17hp 5 speed manual mondial (chinese) engine, with its cdi, cables, gas tank, speedometer, etc.etc.

We began to plan our go-kart:

We planned a suspensioned go kart; but we are not building a buggy. The car's height will be around 9cm, means we can use it in closed-to-traffic roads of Turkey (In Turkey there are many holes and bumps in the roads ) We found a Muravey (a Soviet Triporter) differantial, which has reverse inside. So our kart will also have reverse. Our planned tire end to tire end length is 175cm, and our planned tire end to tire end width is 130cm. Our width in front and width in rear is same. Rear tires are 12-8-6, front tires are 11.5-6-6.

We use rod ends for A arm moves. We have questions about it. We don't know weather rod ends are strong enough or not...

We want to use rack n pinion system; but we want our steering wheel to turn max. 135 degrees (in f1's it is 120 degrees I guess)

If you can make suggestions, about anything you see, it is usable for us!!

 

[s10king91]

what software did you use to make these plans if you care to share with us ?

 

[huseyinozsut]

it is google sketchup!! I found the coilover suspension and rod ends from the online database of sketchup.

know I'm learning solidworks. I want to load some forces on my design! Can anyone help me about tire selection? I want to use 12x8-6 for rears and 11.5x6-6 for fronts. But I don't know which tire to use... for example there are maxxis ht3 a good race tire; but maxxis el is far more durable... Can anyone help me to choose and find a tire?

We also don't know good rim dimensions for both 12x8-6 and 11.5x6-6 (or 11x6-6). For example there are 10" wide rims and I guess they are using it for 12x8-6... So I am a bit confused...

 

[armyvet]

i know maxxis are good tires over here.i used the razors on my atvs..lol i would use tie rod ends from something heavy duty as your a arms mounts/pivots.i wouldnt use them from a atv,dont seem like they would hold up.

 

[redsox985]

Try spindle brackets with large, graded bolts through them. What speeds are you shooting for? If you are staying under about 25-30mph, then most any tire would be ok. ATV and golf cart tires would be the most readily available tire for me at least.

 

[huseyinozsut]

well our aim is 45mph; but that doesn't mean that we will be able to do it! For us, it seems possible. Our engine is out of a chinese chopper, which was around 300lbs. Our go kart won't be more than 300lbs; but will have much higher friction (tire friction, axle and differential). This chinese chopper can make 80mp/h so 45mph in theory is possible... Because of safety reasons we are in search of good tires. We do not want to mount our A arms higher (due to safety reasons, we think at least one of them should be mounted to our main chasis and we also don't want to increase the height of our vertical A arm holding the suspension) If we don't mount A arms higher and use a golf cart or atv tire, then our go karts height will increase very much, which is again a thing we don't want. with 11-7.1-5 tire our max height is 8cm, with 12-8-6 tire our max height is 9.5cm.

I also think to mount the gas tank to the front, between the drivers legs. My engine is abit heaviy, so I want some weight to the front. Also our battery will be there. My question about it: when doing this I will need a gas pump probably. When buying a gas pump, what should I consider? What should its pressure range be?

 

[fowler]

to set up a fuel pump u should make the pump fill a small resovour above the engine so it remans a gravity feed. model engineer pointed out reasons why, i think it is due to the fact it is very hard to tune the pump correctly.
u should make the pump fill the resovour and have a return line back to the tank.

 

[redsox985]

With only 8cm of ground clearance, you will need some very short travel suspension. Suspension works when bumps are encountered and allows the kart to get closer to the ground and if that happens with only 8cm of clearance and raised ground, you will be scraping the bottom.

 

[huseyinozsut]

thank you for resovour suggestion! I'll keep it in mind.

If I manage to increase the ground clearance to 10cm (by the way my car has a ground clearence of 15cm, 2008 ford focus hb), can my suspension at tire can be like 6cm up, 6cm down? Or is it too much? And is 10cm clearance is enough for low quality asphalth?

And probably I should choose a coilover, which will go down the half way when I sit in the cart, so A arms can move up and down equally? Or am I thinking wrong?

 

[fowler]

that sounds like a sound system
but id make sure the ground clearence with u in it is 10cm
also the opgective of suspesion is to keep the vehical as flat as possibe and 10cm is 3.9 inches (for the imperialists) and nothing on the road s that tall. exept speed bumps but u would only crawl across them

 

[huseyinozsut]

In my plan, with me in it, lower A arms are parralel to my chasis and have the same clearence (just like the picture above). My concern is disk brakes... Since I will have differential, I need at least two disc brakes, and since my axle will have u-joints I need to put the breaks just before my tire begins (to not to load excessive force to u-joints). I will find or make small discs, which will have around 8-10cm radius. That means disc brakes will have around 7-8cm clearence to the ground. If I decrease my clearence to 8 cm, discs will have 5-6 cm to the ground, also 6cm of suspension would be a problem I guess... Then I could decrease it to 4cm; but this time isn't it to small?? See, I'm confused a bit!!

Another question is: My kart will be around 300 lbs probably. Most of the karts here are max 240 lbs. and using 11-7.1-5 for rears and 10-4.5-5 for fronts. If I use the same tires for my havier and much stronger kart, probably I'll have issues about cornerning and spinning...

So generally if you can advice me between 12-8-6, 11.5-6-6 and 11-7.1-5, 10-4.5-5 which one would you advice? And what is the ideal clearence and suspension height for me?

I know I ask too much; but I hope other people also can learn something here!! When my plans finish, I will share them here! )

 

[r97]

i don't really have a good answer for the tires (don't worry someone will!), but i do know that some people put a single disc brake on the diff case, instead of one for each wheel.

 

[redsox985]

For handling, incorporate the Ackerman principle. Just google it and you'll catch on easily. Or use the search feature on this site.

 

[huseyinozsut]

I know ackermann principle... If we draw two virtual lines parallel to the arms that we connect our rod-ends, these lines should intersect at the middle point of our axle... But there is also revised ackermann principle, which I should search ... My cart will also have negative camber at kingpin and positive camber at spindle, and KPI.

In most of the cars there is variable camber at the tire (changes according to suspensions position). In most of the cars when we lift them up, the tires' top gets outer from the car, as tire goes down. Normally the resisting force is downward-backward (because of weight and speed of the car); but in turns, it is like downward-outer (outer of the turn). So car's outer part has the most of the load and suspends downward. As outer part suspends, it makes the tire to make a camber degree that the top of the tire is closer to the car. By this, camber the outer tire can resist the downward-outer force better. If I can do the calculations, I also want to apply that to my kart...

All I have is in theory. In real I don't know what will happen when I increase the clearence from 1.5 inch to 4 inch (center of weigth will get higher, bad think for turns) or I don't have an knowledge for ideal positive-negative camber, caster, KPI and variable camber degrees. I'll search them; but I guess it will be like learning by doing!

 

[redsox985]

4in of ground clearance is not much. Your hand, thumb to pinky finger, is probably 8-10in. 4in will not throw off your COG.

 

[huseyinozsut]

ok. Now I have some other problems during planning!

I don't know the ideal maximum angle of tire to take a turn (or is it steering angle?)... Since we have ackermann, camber and caster tires will turn in different angles; but there should be a rough high and low limits. If you can advice something about it, it would be very helpfull for me!

I also couldn't find a front hub, which lets me to connect my tire to one end, a disc to the other end. so I am planning to use these hubs for fronts.

If I use two of these in a row for one tire and connect them with bolts, then I guess I will have a hub which I can connect my brake! As I know we connect our wheels with three bolts. then three bolt holes will be available for me to connect the other wheel hub to my main wheel hub. Or is there a ready to go solution for this?

 

[redsox985]

I'm not sure how you can do it, but those hubs are designed to roll on bearings so they will not work. The rotor bust be attached to the wheel because even the spindle doesn't spin.

 

[huseyinozsut]

Excuse me for my technically-low English! Yes they will turn on bearings; but if I connect two hubs with three bolts (both have 6 holes) and connect one hub to the wheel with three bolts, I'll have the inner hub to spin together with tire... Then if I connect my disc to the inner hub, although they spin on bearings, since they are to each other with bolts...

I found a 5 bolt hub on database of sketch up, imagine that the drawing here is the hub I found...

So three bolts will connect the two hubs, one hub will be connected to tire and the other will be connected to disc... Is it ok? Or is there any ready hubs which I can connect both disc and tire?

And also what should be the max steering angle in optimal? At least is there a range?

 

[redsox985]

That may be rather long being that those hubs are made to fit on a spindle. 2 may be too long.

 

[pmichelsen]

This is what you need...

Found at:

www.cometkartsales.com